My ~2450fps 350gr hornady snrn .458 loads stay inside an inch at 100yds over the iron sights, never got around to pushing the load for more velocity, but my sense and feel is that the rifle would be just as happy with another hundred fifty fps.

I'm happy with that load though, it's just fine inside the range of my express sights - 1/2/300yds

Cheers
Tinker